This application relates to devices, techniques and systems for detecting heart rates using an optical sensor.
In a typical optical heart rate sensor, a photodiode, a low noise amplifier and an analog to digital converter (ADC) can be used to measure the photodiode response with a LED with different wavelength as light source. The sensitivity of the optical sensor to background light and motion of the user can cause significant interferences of measurements. The low noise amplifier usual requires more power, and the useful heart rate signals usually is only 100th to 10,000th of the total photodiode signals.